The gist of the book is that the coalition of religious conservatives and libertarian free-marketeers is breaking apart. The basic principle that held them together throughout the postwar era — the idea that morality and virtue need to be freely chosen to have meaning — is breaking down. The traditionalists have gotten the upper hand and increasingly reject the idea of freedom when it comes to things like gay marriage, pornography, drugs and abortion.

The traditionalists, infused by evangelical religious fervor, have taken that wing of the party far beyond its historical roots. In the past, traditionalists were religious and pro-religion, but highly tolerant of those non-religious conservatives who derived their ideology from natural law or free-market economic principles. Thus traditionalists like William F. Buckley and Russell Kirk could coexist with atheists like Ayn Rand and Ludwig von Mises. They respected each other’s views even if they disagreed with their foundation.

The traditionalist-libertarian coalition was also a political marriage of convenience. Neither group commanded sufficient votes to defeat the liberals, who were dominant from the 1930s to the 1970s. Since liberalism was abhorrent to both groups, they were able to make common cause.

Traditionalists hated the militant secularism of the liberals, who sought to banish religion from the public square, and their scorn for traditional values and ways of doing things, whether in the schools, the churches, the culture or within the family itself. The 1960s were a watershed when liberalism expanded far beyond economics, where it was largely confined during the Roosevelt era, to embrace feminism, drugs, and free love, combined with utter disdain for order and the institutions that sustained it.

So extreme was the revolt against tradition in the 1960s that many New Deal liberals believed the New Left was threatening to bring down civilization itself in an orgy of nihilism. Feeling they had been mugged by reality, a number ended up switching sides, becoming neoconservatives.

Meanwhile, the libertarians were empowered by the collapse of Keynesian economics in the 1970s. John Maynard Keynes had argued that government deficits were stimulative. When this idea appeared to work during World War II, the old balanced-budget constraint was abandoned. This opened the door to a vast increase in government spending, which reached a pinnacle during Lyndon Johnson’s Great Society.

But when inflation became a serious problem in the 1970s, the Keynesians really had no good explanation for it or a cure. In this intellectual vacuum, libertarian economists like Milton Friedman gained credibility and influence by arguing that tight money was needed to stop inflation.

The Keynesians also had little to offer when economic growth slowed to a crawl. It wasn’t plausible to advocate deficit spending when the budget was already hemorrhaging red ink and interest rates and inflation were shooting through the roof. This opened the door for the supply-siders, who advocated tax rate reductions to stimulate growth. Skeptics of this idea were silenced when the voters of California approved Proposition 13 in 1978, which slashed property taxes in that state, triggering a national tax revolt.

By 1980, these different strands of the conservative coalition united behind Ronald Reagan, who skillfully pulled them together under the Republican tent. By 1994, the coalition was strong enough to gain control of Congress, and Republicans truly became the nation’s governing party for the first time since 1932.

Sager argues that George W. Bush has effectively destroyed this extremely successful political partnership by siding with the traditionalists and ignoring the libertarians. He threw a few tax cuts at the latter, like bones to a dog, but at the same time endorsed a vast expansion of government spending that will soon lead inevitably to tax increases.

Bush’s courting of the evangelicals has increased friction between them and the libertarians, who now have become deeply alienated from the Republican Party, Sager argues. They may not be ready to become Democrats, but neither can the libertarians be considered a reliable part of the Republican coalition any longer, as they were in the Reagan era.

Sager believes that this spells doom for the Republicans unless a new leader emerges around whom the libertarians can rally. He suggests that Rudy Giuliani may be the one, but that remains to be seen. In the meantime, Sager thinks the libertarians are likely to disengage from politics and just sit out the next election.

I think he is right, and it’s a key reason why I think Republicans are going to do very poorly in November. When they look for ways to pick up the pieces afterward, Sager’s book will be a useful guide.